Method and apparatus for uplink rate selection in the presence of multiple transport channels in a wireless communication system

ABSTRACT

Systems and methods for selecting data rates at which to transmit data over a primary uplink in the presence of one or more secondary uplink channels. One embodiment comprises a method including determining probabilities associated with numbers of attempted transmissions of data, determining the number of times pending data transmissions have been attempted, determining probabilities associated with the data transmissions, and allocating power for transmission of the data in a succeeding frame based upon the associated probabilities. In one embodiment, a highest supportable data rate for a primary uplink is initially selected. Then, power is allocated for a minimum set of channels on the primary uplink. Then, power is allocated for pending data transmissions on the secondary uplink. A maximum power level for the transceiver is then adjusted to account for the allocated power, and the highest supportable data rate for the primary uplink is recomputed.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent claims priority to ProvisionalApplication No. 60/496,952 entitled “Method and Apparatus for UplinkRate Selection in the Presence of Multiple Transport Channels in aWireless Communication System” filed Aug. 20, 2003, and assigned to theassignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

1. Field

The present invention relates generally to communication systems, andmore particularly, to systems and methods for uplink rate selection inthe presence of multiple transport channels in a wireless communicationsystem.

2. Background

An exemplary wireless telecommunications system may be designed inaccordance with the 3GPP standard, Release 99, which is known to thoseof skill in the art and is hereby incorporated by reference. In thissystem, a base station controller is coupled to a plurality of basetransceiver stations, or base stations. There may be many base stationsthat are coupled to the base station controller. The base stationcontroller is typically coupled to the base stations through a networkthat is typically referred to as the backhaul network.

Each base station is capable of communicating with a plurality of mobilestations that are within a coverage area associated with the basestation. Again, there may be many mobile stations in the base station'scoverage area that are communicating with the base station. The mobilestation communicates with the base station via a wireless link. Thewireless link includes a set of channels for communicating data from thebase station to the mobile station, as well as a set of channels forcommunicating data from the mobile station to the base station. Thefirst set of channels (from base station to mobile station) are referredto as the forward link. The second set of channels (from mobile stationto base station) are referred to as the reverse link.

In this system, when the mobile station has data that it needs totransmit to the base station, a request is transmitted from the mobilestation to the base station. This request is a request for permission totransmit the mobile station's data to the base station. After the basestation receives the request, it may issue a grant to the mobile stationin response to the request. The grant allows the mobile station totransmit data to the base station at up to a specified maximum data ratefor an allotted interval.

When the grant is received by the mobile station, the mobile stationdetermines an appropriate rate at which to transmit its data, and thentransmits the data over a dedicated data channel at the selected rateduring the allotted interval. The mobile station selects a data rate atwhich to transmit data on the dedicated data channel based in large parton its power constraints. For example, in this system, the mobilestation has a maximum power (e.g., 125 milliwatts) with which it cantransmit its data, so a data rate is selected that is not expected tocause the mobile station to exceed its maximum power level. In thissystem, the mobile station's history (with respect to the amount ofpower required to transmit at a given data rate) is viewed to determinethe maximum allowable data rate corresponding to a power level that isbelow the maximum level.

This simple method of selecting a data rate, however, accounts for onlya single channel (the dedicated data channel) and does not provide anacceptable methodology for rate selection if the mobile station will betransmitting data over multiple channels. It would therefore bedesirable to provide systems and methods for selecting data rates in thepresence of multiple channels.

SUMMARY

Embodiments of the invention which are disclosed herein address one ormore of the needs indicated above by providing a mechanism for selectingdata rates at which to transmit data over a primary uplink in thepresence of one or more secondary uplink channels.

One embodiment comprises a method implemented in a remote transceiver ofa wireless communication system, wherein the transceiver is configuredto retransmit pending data on a secondary uplink until the data isacknowledged or until a maximum number of retransmissions are made. Themethod includes determining probability values associated with thenumbers of attempted transmissions of the data and, for each of aplurality of pending data transmissions, determining the number of timestransmission of the data has been attempted, determining a probabilityassociated with the number of attempts, and allocating power fortransmission of the data in a succeeding frame based upon theprobability associated with the number of transmission attempts.

In one embodiment, the method includes initially selecting a highestsupportable data rate for a primary uplink using a conventionalmethodology. In this methodology, the data rate is selected bydetermining which data rates would have been supported in a set ofpreceding frames and then selecting the highest of these rates. Afterthe initial data rate for the primary uplink is determined, power isallocated for a minimum set of channels on the primary uplink. Then,power is allocated for pending data transmissions on the secondaryuplink. A maximum power level for the transceiver is then adjusted toaccount for the allocated power, and the highest supportable data ratefor the primary uplink is recomputed.

An alternative embodiment comprises a transceiver configured tocommunicate data via a wireless communication link. In this embodiment,the transceiver is configured to retransmit pending data on a secondarychannel until the data is acknowledged or until a maximum number ofretransmissions are made. The transceiver is further configured todetermine probability values associated with one or more numbers ofattempted data transmissions. Then, for each of a plurality of pendingdata transmissions, the transceiver determines a number of times thedata transmission has been attempted in one or more preceding frames,determines a probability associated with the number of times the datatransmission has been attempted, and allocates power for the datatransmission in a succeeding frame based upon the probability associatedwith the number of times the data transmission has been attempted.

Yet another alternative embodiment comprises a storage medium, readableby a processor, which contains program instructions to cause theprocessor to perform a method as described above. In one embodiment, theprocessor is a component of a wireless transceiver, and the instructionson the storage medium configure the processor to determine probabilityvalues associated with numbers of attempted data transmissions and, foreach of a plurality of pending data transmissions, determine a number oftimes the data transmission has been attempted, determine a probabilityassociated with the number of attempts, and allocate power for the datatransmission in a succeeding frame based upon the probability associatedwith the number of transmission attempts.

Numerous alternative embodiments are also possible.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and features of the invention are disclosed by thefollowing detailed description and the references to the accompanyingdrawings, wherein:

FIG. 1 is a diagram illustrating the structure of a wirelesstelecommunications system in accordance with one embodiment;

FIG. 2 is a diagram illustrating the power used by a mobile station totransmit data to a base station in one embodiment;

FIG. 3 is a diagram illustrating the timing of transmissions over thechannels of the enhanced uplink in accordance with one embodiment; and

FIG. 4 is a flow diagram illustrating a method in accordance with oneembodiment.

While the invention is subject to various modifications and alternativeforms, specific embodiments thereof are shown by way of example in thedrawings and the accompanying detailed description. It should beunderstood, however, that the drawings and detailed description are notintended to limit the invention to the particular embodiments which aredescribed.

DETAILED DESCRIPTION

One or more embodiments of the invention are described below. It shouldbe noted that these and any other embodiments described below areexemplary and are intended to be illustrative of the invention ratherthan limiting.

As described herein, various embodiments of the invention comprisesystems and methods for selecting data rates at which to transmit dataover a primary uplink in the presence of one or more secondary uplinkchannels. In one embodiment, a wireless communications system usesmultiple channels to transmit data between a base station and a mobilestation. The channels include multiple forward link channels fortransmitting data from the base station to the mobile station, as wellas multiple reverse link channels for transmitting data from the mobilestation to the base station. The mobile station in this system takesinto account historical information, as well as expected requirements,relating to data rates and transmission power in order to select datarates at which to transmit data to the base station via the reverse linkchannels.

In this embodiment, the mobile station determines which of a set ofpossible data rates are supported for a first (e.g., dedicated data)channel, based on data transmissions in a preceding frame interval andthe relationship of these transmissions to a maximum power level. Themobile station also determines estimated power requirements for a second(e.g., enhanced uplink) channel, based upon transmissions that areexpected to be made on this channel in an upcoming frame. The mobilestation then reserves power for a minimum set of channels that are to betransmitted on the first channel, reserves power for the data expectedto be transmitted on the second channel, and computes the highest datarate that can still be supported on the first channel after power isreserved for the data to be transmitted on the second channel.

One embodiment of the invention is implemented in a wirelesstelecommunications system that is designed in accordance with variousreleases of the 3GPP standard, including Release 99 and Release 6. Itwill therefore be helpful to describe the basic structure and operationof such a system in order to aid in the understanding of the invention.It should be noted that, while the following description focusesprimarily upon a system that follows this standard, alternativeembodiments may be implemented in systems that follow other standards aswell.

Referring to FIG. 1, a diagram illustrating the structure of a wirelesstelecommunications system in accordance with one embodiment is shown.System 100 includes a base station controller 110, a base station 120that is coupled to base station controller 110 through a backhaulnetwork 130, and a mobile station 140. System 100 may include additionalbase stations and mobile stations which, for purposes of clarity, arenot shown in the figure.

The terminology used to refer to the components of the system differsslightly in the various releases of the 3GPP standard. For example, basestation controller 110 may be referred to as a radio network controller(RNC), base station 120 may be referred to as a “Node B,” and mobilestation 140 may be referred to as user equipment (UE). Because thevarious embodiments of the invention may be implemented in differenttypes of wireless communication systems (e.g., systems designedaccording to different standards or different releases of the samestandard,) references to the different components of the systems shouldbe interpreted broadly, and references to particular components usingterminology applicable to a particular type of system should not beconstrued to imply that the embodiments of the invention are limited tothat particular type of system.

Referring again to the system depicted in FIG. 1, if mobile station 140has data that needs to be transmitted to base station 120, it transmitsa request to base station 120, asking for authorization to transmit thisdata. In response to the request, base station 120 may transmit a grantto mobile station 140. The grant authorizes mobile station 140 totransmit data to base station 120 at up to a specified data rate. Aftermobile station 140 receives the grant, it may begin transmitting data tobase station 120 during a succeeding radio frame.

Mobile station 140 typically is not stationary (although, in someinstances, it may be.) Mobile station 140 is instead likely to move withrespect to base station 120. The changing position of mobile station 140typically causes the channel conditions for the wireless link betweenmobile station 140 and base station 120 to vary. The channel conditionsmay also be affected by other factors, such as atmospheric conditions,movement of other objects between mobile station 140 and base station120, interference from other transmitters, and so on.

It should be noted that, while the description herein of this and otherembodiments focuses on a system in which a mobile station may move withrespect to a base station, other embodiments may be implemented insystems that enable wireless communication between alternative types ofdevices. It is not necessary that one of the devices be a “basestation,” nor is it necessary that the other of the devices be “mobile.”References herein to mobile stations and base stations should thereforebe construed to include any wireless transceiver devices that are incommunication with each other.

Because of the changes in the channel conditions for the wirelesscommunication link, there may be changes in the data rate at whichmobile station 140 transmits data to base station 120. These changes inthe data rates used by mobile station 140 to transmit the data arenecessary to provide a high enough signal-to-noise ratio, SNR, (orsignal-to-interference-and-noise ratio, SINR,) that base station 120will receive the data with an acceptable error rate. The better thechannel conditions, the higher the data rate that can be used by themobile station. The worse the channel conditions, the lower the datarate that typically needs to be used by the mobile station.

The data rate at which mobile station 140 can transmit data is limitednot only by the channel conditions, but also by the power constraints ofthe mobile station. The power required to transmit data at a particularrate is proportional to the data rate. Thus, it takes less power totransmit at a lower data rate than is needed to transmit data at ahigher data rate. This is important because mobile station 140 istypically allowed to transmit data at or below a maximum power level.For instance, in one embodiment, mobile stations are allowed to transmitdata using up to a maximum of 125 milliwatts.

In Release 99, the data rate for a particular channel is also referredto as a transport format (TF). Because the dedicated physical datachannel of Release 99 actually includes multiple logical or virtualchannels, a particular combination of data rates (or transport formats)for these channels is referred to as the transport format combination(TFC). For purposes of clarity, individual transport formats as well astransport format combinations will be referred to below simply as datarates.

The data rate for a particular channel is equal to the amount of data tobe transmitted, divided by the transmit time interval, or TTI. Themobile station selects suitable data rates (a TFC) for the uplinkchannels from the set of possible data rates at each boundary betweenten millisecond radio frames. The various possible TFCs can becollectively referred to as the TFC set, or TFCS.

As noted above, there are limitations on the amount of power that can beused by mobile station 140 to transmit data. There is therefore acorresponding limit on the rates at which the data can be transmitted.If the power that is required to transmit data at a particular rate (orwith a particular TFC) does not exceed the maximum allowable powerlevel, then that particular data rate is supported within the powerconstraints of the mobile station. In other words, a mobile stationoperating at or below its maximum allowable power can support datatransmissions at that data rate. If, on the other hand, transmittingdata at that particular rate will cause the mobile station to exceed itsmaximum power level, the data rate is, generally speaking, notsupported.

Referring to FIG. 2, a diagram illustrating the power used by a mobilestation to transmit data to a base station in one embodiment is shown.In this embodiment, data is transmitted from mobile station 140 to basestation 120 over a ten millisecond radio frame 210. The data istransmitted using a selected data rate (TFC,) and a corresponding amountof power is used to transmit the data at this rate. Curve 211 indicatesthe the power actually used by mobile station 140 to transmit the data.It can be seen that the power used to transmit the data varies over theinterval covered by frame 210 to compensate for variations in thechannel conditions. The power used by mobile station 140 does not exceedthe mobile station's maximum power level (indicated by dashed line 230).The particular data rate used by mobile station 140 to transmit the datais therefore supported.

The question of whether a particular data rate can be supported in thenext frame cannot be answered with certainty because the data has yet tobe transmitted, and it cannot be known with certainty what the channelconditions will be in the future (i.e., when the data is actuallytransmitted.) The determination of whether or not each possible datarate is supported is therefore based upon the recent history of themobile station's data transmissions. More specifically, the mobilestation examines the amount of power that was required to transmit dataat a particular rate during a previous interval, and makes theassumption that the channel conditions and corresponding powerrequirements for each data rate will be approximately the same. Thus, ifa data rate was supported during the previous interval, it is assumedthat the data rate will be supported during the succeeding interval.

Referring again to FIG. 2, several different curves are depicted withinframe 210. As noted above, curve 211 illustrates the power actually usedby mobile station 140 to transmit data during the frame. As also notedabove, this curve is below maximum power level 230, so the correspondingdata rate is considered to be supported. Curves 212, 213 and 214illustrates the power that would have been used to transmit the samedata under the same channel conditions, but at different data rates.Curves 212 and 213 correspond to lower data rates and consequently wouldhave required less power to transmit the data. These data rates aretherefore supported. Curve 214, on the other hand, corresponds to ahigher data rate than was actually used and would have required morepower. As shown in the figure, this curve is entirely above maximumpower level 230, and therefore would not have been supported.

In Release 99, ten millisecond frames are used to transmit data. TheRelease 99 standard specifies that the mobile station will examine thepower of the data transmissions during the previous twenty millisecondsand, based upon this information, will determine whether each of thepossible data rates (TFCs) is supported. In the example of FIG. 2, thedata rates corresponding to curves 211–213 are supported, while the datarate corresponding to curve 214 is not. The mobile station will thenselect the highest of the supported data rates (211 in this example)and, if the selected data rate is less than or equal to the maximum ratespecified in a grant from the base station, this highest supported ratewill be used to transmit data during the next ten millisecond frame (asshown by curve 240.) If the highest supported data rate is greater thanthe maximum rate specified in the grant, the mobile station will selectthe highest of the supported data rates that is less than or equal tothe maximum rate specified in the grant.

This scheme for selecting the data rate at which the mobile station willtransmit data to the base station is a straightforward and is suitablefor implementation in Release 99 because there is only a single,dedicated channel on which data will be transmitted. This is the onlychannel that needs to be considered in determining the rate at whichdata can be transmitted. In a system designed according to a laterrelease of this standard (Release 6,) however, an enhanced uplink isdefined. The enhanced uplink includes additional reverse-link channelson which data can be transmitted from the mobile station to the basestation. In order to enable the mobile station to transmit data overthis additional channel, while remaining within the power constraints ofthe mobile station, it is desirable to take the additional channel intoaccount when selecting a data transmission rate.

If the additional channels of the enhanced uplink were managed in thesame way as the dedicated data channel of the Release 99 uplink, itmight be possible to use a scheme similar to the one described above toselect a data transfer rate. That is, it might be possible to assumethat channel conditions will be the same as in the recent history of themobile station, and to allocate power for the data to be transmittedbased upon the history of the channel conditions. The channels of theenhanced uplink, however, are not used in the same way as the channelsof the Release 99 uplink. Some of these differences are explained belowwith respect to FIG. 3.

Referring to FIG. 3, a diagram illustrating the timing of transmissionsover the channels of the enhanced uplink is shown. Reference number 300indicates the transmissions of data from the mobile station to the basestation on the enhanced uplink, while reference number 310 indicatestransmissions from the base station to the mobile station via adownlink.

In this embodiment, the enhanced uplink channels include an enhanceddata channel (E-DCH), a rate indicator channel (RICH), a request channel(REQCH) and a secondary pilot channel (SPICH). It can be seen from thefigure that in one embodiment the enhanced uplink channels use twomillisecond subframes, rather than the ten millisecond frames used bythe Release 99 data channels. Each two millisecond subframe has threeslots, for a total of 15 slots in each frame. The enhanced data channelmay be transmitted by HARQ (hybrid automatic repeat request) processesin each two millisecond subframe. Rate indicator information can betransmitted corresponding to each of the HARQ processes. If a request istransmitted by the mobile station, it is transmitted via the requestchannel during the first two millisecond subframe within the tenmillisecond frame.

The enhanced uplink implements a hybrid automatic repeat request, orHARQ, mechanism. This mechanism is used by the mobile station toautomatically repeat transmissions of data that are not acknowledged bythe base station. The series of transmissions of a frame of datacomprise a HARQ process. Thus, in a HARQ process, when data istransmitted from the mobile station to the base station using the datachannel of the enhanced uplink, the base station receives the data,decodes the data and then transmits an acknowledgment (ACK) to themobile station. When the mobile station receives the acknowledgment, itknows that the data that it transmitted to the base station wassuccessfully received and decoded. In this case, the mobile station isdone with the transmitted data (i.e., the HARQ process is terminated.)

If, on the other hand, the base station receives, but does notsuccessfully decode the data, the base station will transmit anon-acknowledgment (NAK) to the mobile station. When the mobile stationreceives the non-acknowledgment, it knows that the data was notsuccessfully received and decoded. The mobile station must thereforere-transmit this data (i.e., the HARQ process is continued.) The same istrue if neither an acknowledgment or a non-acknowledgment is received bythe mobile station. In one embodiment, the mobile station will attemptto re-transmit the data a predetermined number of times. If thetransmission is still unsuccessful after the predetermined number ofre-transmissions, the data will be dropped, terminating the HARQprocess.

There are several factors that complicate the selection of a suitabledata rate for transmission of data on the enhanced uplink. One suchfactor is that the presence or absence of each of the enhanced uplinkchannels is probabilistic. In other words, each of these channels may ormay not be used in a given frame. For example, it may or may not benecessary in the next frame to transmit a request to the base stationvia the request channel.

Another, related complicating factor is the implementation of the HARQmechanism. As pointed out above, this mechanism provides for theautomatic retransmission of data that is not acknowledged by the basestation as having been successfully received and decoded. This isproblematic because the successful receipt of data cannot be immediatelyacknowledged. Time is required to transmit the corresponding data fromthe mobile station to the base station, to decode the data, to determinethat the data has been successfully received and decoded, and totransmit an acknowledgment back to the mobile station. This delay isillustrated in FIG. 3.

As shown in FIG. 3, HARQ process 0 is transmitted by the mobile stationin the first two millisecond slot of frame f. The acknowledgment of HARQprocess 0 is received approximately 3½ slots (seven milliseconds) later.Thus, in the case of HARQ process 0, the acknowledgment is receivedwithin the span of frame f. The mobile station therefore knows whetherit will need to retransmit the data of HARQ process 0 when the data rateis selected at the boundary between frames f and f+1. This is not aproblem. The problem relates to the acknowledgment of HARQ processes1–4. The acknowledgment of any of these HARQ processes cannot bereceived within the same frame. As a result, when a data rate isselected at the boundary between frames f and f+1, it is not knownwhether any of HARQ processes 1–4 was successfully received by the basestation. The mobile station therefore does not know whether or not itneeds to retransmit the corresponding data. The mobile station can onlyguess as to whether this data needs to be transmitted and how much powermight need to be allocated to these transmissions.

At each frame boundary, the mobile station knows only whether thefollowing channels will be transmitted in the succeeding frame: E-DPDCH,RICH and SPICH for HARQ process 0; if REQCH and E-DPDCH was nottransmitted during slots 3–14 of frame f, then the E-DPDCH, RICH andSPICH will not be transmitted during the corresponding slots of frame(f+1); if REQCH was transmitted during slots 3–14 of frame f, then theE-DPDCH, RICH and SPICH could be transmitted during the correspondingslots of frame (f+1); and if E-DPDCH was transmitted during slots 3–14of frame f and the transmission was not the last one, then the E-DPDCH,RICH and SPICH could be re-transmitted during the corresponding slots offrame (f+1).

Because the mobile station does not know whether or not any other datawill be transmitted on the enhanced uplink channels, the simple datarate selection scheme used for the Release 99 uplink cannot be directlyapplied. If assumptions about the enhanced uplink transmissions aremade, however, this scheme can be applied. For instance, it can beassumed that no data will be transmitted on the enhanced uplink channelsin the next frame. The problem with this assumption is that the mobilestation may not be able to make necessary transmissions of data on theenhanced uplink channels. Conversely, it can be assumed that all of thepossible enhanced uplink channel transmissions are made in each frame.The problem with this assumption is that the enhanced uplink channelsare not always needed, so some of the enhanced uplink bandwidth isunused, while the Release 99 uplink channels may not have enoughbandwidth. It therefore appears that an assumption which is intermediateto these two extremes would be most reasonable.

One embodiment implements a scheme that takes into account theprobabilistic nature of the HARQ retransmissions. For the portions ofthe data transmissions that are not known, this scheme makes an estimateof the amount of data that will be transmitted. Similar to the Release99 scheme, the estimate is based on historical information, but thehistorical information does not concern the channel conditions. Instead,the historical information concerns the HARQ retransmissions of thedata.

As noted above, the data for a particular HARQ process is transmittedfrom the mobile station to the base station and, if the transmission isnot acknowledged, the data is re-transmitted. In this embodiment, theretransmissions are tracked to identify the probability with which eachHARQ process will be retransmitted. More specifically, the long termresidual block error rate (BLER) is tracked. For each transmission (orretransmission,) there is a corresponding probability that the data willneed to be transmitted again in the next frame.

For example, for each HARQ process that has been transmitted only oncemay have a 90% probability of having to be transmitted again. For eachHARQ process that has been transmitted twice, the probability ofretransmission may be 50%. Each succeeding number of transmissions hasan associated probability of transmission in the next frame. Generallyspeaking, the more times transmission of a HARQ process has beenattempted, the lower the likelihood will be that this process will needto be transmitted again in the next frame. As noted above, the number oftransmissions is limited, so after the last transmission, theprobability of transmitting the data again in the next frame will be 0.

The mobile station uses this probability information to determinewhether each of the non-acknowledged HARQ processes will need to beretransmitted. For each of these processes, the mobile stationdetermines the number of times that process has been transmitted,determines the probability associated with this number of transmissions,and either allocates or does not allocate power for transmission of thisprocess based upon the associated probability.

Thus, for example, assume that retransmission of each HARQ process willbe attempted up to four times. Assume further that the probabilitiesthat these processes will need to be transmitted in next frame is asshown in the table below.

probability process will No. of times process have to be transmitted hasbeen transmitted in the next frame 0 100% 1  90% 2  50% 3  15% 4  0%

If data for a particular HARQ process has not yet been transmitted fromthe mobile station to the base station, the probability that thisprocess will need to be transmitted in the next frame is 100%. Themobile station therefore allocates power for transmission of thisprocess. If, on the other hand, the HARQ process being considered hasalready been transmitted once, the probability that the process willneed to be transmitted again in the next frame is only 90%. The mobilestation will therefore allocate power for transmission of this processwith a 90% probability. If the data corresponding to the process hasbeen transmitted four times, no power will be allocated to transmit thisdata again.

The allocation of power with a particular probability does not mean thatthe mobile station will allocate only a portion of the power requiredfor transmission of the process. Instead, the mobile station will eitherallocate all of the power required for the transmission or none of therequired power. For example, when there is a 90% chance the data willneed to be retransmitted, the mobile station will allocate power 90% ofthe time, and will not allocate power 10% of the time. In oneembodiment, this is accomplished by generating a random number between 0and 1, and then allocating power for the process if the generated numberis between 0 and 0.9, or not allocating power for the process if thegenerated number is between 0.9 and 1.

Because, in the embodiment described above, the mobile station transmitsdata on both the enhanced uplink channels and the release 99 uplinkchannels, this power allocation scheme for the enhanced uplink is usedin conjunction with a modified version of the Release 99 data rateselection scheme. The resulting scheme is illustrated in FIG. 4.

Referring to FIG. 4, a flow diagram illustrating a method in accordancewith one embodiment is shown. In this embodiment, the mobile stationfirst determines the highest supported data rate (block 410.) The mobilestation then determines the amount of power that will be needed totransmit pending HARQ processes on the enhanced uplink (block 420.) Themobile station then reserves power for a “minimum set” of channels onthe Release 99 uplink, reserves power for the pending HARQ processes asdetermined in block 420, and then determines the highest data rate thatis still supported after power is reserved for the pending HARQprocesses on the enhanced uplink (block 430.)

Determining the highest supported data rate in block 410 is performed inthe conventional manner. In other words, information on the previous tenmillisecond frame is examined and to the highest supportable data ratefor the data channels is determined. This is the same scheme as is usedin Release 99. The enhanced uplink channels are ignored for the purposeof determining the highest supportable data rate. This is the samescheme as is used in Release 99, so this embodiment isbackwards-compatible with systems based on Release 99.

In Release 99, the mobile station selects a TFC from its current TFCSwhenever it has data to transmit in the uplink. The TFC is selectedbased on the data in the mobile station's buffer, the currentlyavailable transmission power, the available TFCS and the mobilestation's capabilities.

Each TFC in the available TFCS is in one of three states: supported;excess-power; or blocked. A TFC in the supported state can be used fortransmission of data in the uplink. A TFC in the excess-power statewould require more than the maximum allowable power, and consequentlywill not be selected for transmission of data in the uplink. A TFC inthe blocked state likewise requires too much power, and will not beselected for uplink transmissions.

Based on certain parameters, the mobile station continuously evaluateselimination, recovery and blocking criteria according to which TFCs canmove between the supported, excess-power and blocked states. The mobilestation considers the elimination criteria for a TFC if the estimatedmobile station transmit power needed for this TFC is greater than themaximum mobile station transmitter power for at least a certain portionof a number of slots immediately preceding evaluation. The mobilestation considers this TFC to be in an excess-power state. The mobilestation considers the blocking criteria for a TFC if it stays in theexcess-power state for a certain period of time. The mobile stationconsiders the recovery criterion for a TFC if the estimated mobilestation transmit power needed for this TFC has not been greater than themaximum mobile station transmitter power for a certain number of slotsimmediately preceding evaluation. The mobile station considers this TFCto be in the supported state.

In block 420, the mobile station determines the power requirements forthe enhanced uplink. This includes determining the power requirementsfor the data that the mobile station knows will be transmitted (e.g.,retransmissions of pending HARQ process 0,) as well as determining powerrequirements for data that may or may not be transmitted (e.g.,retransmissions of pending HARQ processes 1–4.) The power requirementsdetermined in this embodiment are the average power requirements over aframe, rather than the peak power.

The amount of power that is expected to be used to transmit data on theenhanced uplink is computed in the following manner. First, severalvariables are defined.

$\begin{matrix}{f = {{Frame}\mspace{14mu}{number}}} \\{m = {{Slot}\mspace{14mu}{number}}} \\{= {{15 \cdot f} + s}} \\{0 \leq s \leq 14} \\{H = {{Number}\mspace{14mu}{of}\mspace{14mu}{HARQ}\mspace{14mu}{processes}}}\end{matrix}$

Further, several functions are defined.P_(s)(k; f)=DPCCH Transmit power during slot k of frame f,

-   -   where DPCCH is a dedicated physical control channel of the        Release 99 uplink

$\begin{matrix}{{P(f)} = {{Average}\mspace{14mu}{DPCCH}\mspace{14mu}{Transmit}\mspace{14mu}{power}\mspace{14mu}{for}\mspace{14mu}{frame}\mspace{14mu} f}} \\{= {\frac{1}{15} \cdot {\sum\limits_{k = 0}^{14}\;{P_{s}\left( {k;f} \right)}}}} \\{{{P_{av}(f)} = {{Moving}\mspace{14mu}{average}\mspace{14mu}\left( {{over}\mspace{14mu} F\mspace{14mu}{frames}} \right)\mspace{11mu}{of}\mspace{14mu}{DPCCH}\mspace{14mu}{Transmit}}}{\mspace{11mu}\mspace{31mu}}} \\{{\;}{{power}\mspace{14mu}{at}\mspace{14mu}{frame}\mspace{14mu} f}} \\{= {\frac{1}{F} \cdot {\sum\limits_{k = 0}^{F - 1}\;{P\left( {f - k} \right)}}}}\end{matrix}$

During frame f, the mobile station either sends a request or transmitsE-DPDCH (the dedicated physical data channel of the enhanced uplink,) orboth. The transmission during frame (f+1) depends upon this.

We then define several additional variables.

$\begin{matrix}{{I_{r}\left( {j;f} \right)} = {{REQCH}\mspace{14mu}{Indicator}\mspace{14mu}{function}\mspace{14mu}{for}\mspace{14mu}{HARQ}\mspace{14mu}{process}\mspace{14mu} j}} \\{{during}\mspace{14mu}{frame}\mspace{14mu} f} \\{= \left\{ \begin{matrix}0 & {{No}\mspace{14mu}{request}} \\\phi & {{Request}\mspace{14mu}{made}}\end{matrix} \right.} \\{0 \leq \phi \leq 1} \\{{{r\left( {j;f} \right)} = {{Requested}\mspace{14mu} E\text{-}{DPDCH}\mspace{14mu}{TF}{\mspace{11mu}\;}{for}\mspace{14mu}{HARQ}{\mspace{11mu}\;}{process}\mspace{14mu} j\mspace{14mu}{during}}}\mspace{20mu}} \\{{frame}\mspace{14mu} f} \\{{I_{t}\left( {j;f} \right)} = {E\text{-}{DPDCH}\mspace{14mu}{Transmission}\mspace{14mu}{Indicator}\mspace{14mu}{function}\mspace{14mu}{for}\mspace{14mu}{HARQ}}} \\{{process}\mspace{14mu} j\mspace{14mu}{during}\mspace{14mu}{frame}\mspace{14mu} f} \\{\left\{ \begin{matrix}0 & {{No}\mspace{14mu}{transmission}\mspace{14mu}{or}\mspace{14mu}{last}\mspace{14mu}{re}\text{-}{transmission}} \\1 & {{Transmission}\mspace{14mu}{made}\mspace{14mu}{and}\mspace{14mu}{could}\mspace{14mu}{potentially}} \\\; & {\;{{re}\text{-}{transmit}}}\end{matrix} \right.} \\{{\chi\left( {j;f} \right)} = {E\text{-}{DPDCH}{\mspace{11mu}\;}{TF}\mspace{14mu}{for}\mspace{14mu}{HARQ}\mspace{14mu}{process}\mspace{14mu} j\mspace{14mu}{during}\mspace{14mu}{frame}\mspace{14mu} f}}\end{matrix}$

To compute the estimate of average required transmit power during frame(f+1), we have:p(l)=Residual E-DPDCH BLER after l transmissions 1≦l≦N_(max)−1N_(max)=Maximum number of transmissions allowedN_(e)(j;f)=E-DPDCH transmission number for HARQ process j during frame f

Further, we define the amplitude scaling factors as:β_(d,i)=Scaling factor for DPDCH TFC iβ_(e,i)=Scaling factor for E-DPDCH TF iβ_(c)=Scaling factor for DPCCHβ_(θ,i)=Scaling factor for RICH+SPICH for E-DPDCH TF i

The weighted probability of request and re-transmission can be writtenas:

$\begin{matrix}{{q\left( {j;f} \right)} = \frac{p\left( {N_{e}\left( {j;f} \right)} \right)}{{\sum\limits_{j = 0}^{H - 1}\;{p\left( {N_{e}\left( {j;f} \right)} \right)}} + \phi}} \\{\xi = \frac{\phi}{{\sum\limits_{j = 0}^{H - 1}\;{p\left( {N_{e}\left( {j;f} \right)} \right)}} + \phi}}\end{matrix}$

To compute the maximum requested rate, define:

$\begin{matrix}{{S_{r}(f)} = \left\{ {j:{{{I_{r}\left( {j;f} \right)} \cdot \left( {1 - {I_{t}\left( {j;f} \right)}} \right)} > {0\mspace{14mu}{\forall{0 \leq j \leq {H - 1}}}}}} \right\}} \\{= {{Set}\mspace{14mu}{of}\mspace{14mu}{HARQ}\mspace{14mu}{processes}\mspace{14mu}{for}\mspace{14mu}{which}\mspace{14mu}{REQCH}\mspace{14mu}{was}}} \\{{{transmitted}\mspace{14mu}{during}\mspace{14mu}{frame}\mspace{14mu} f\mspace{14mu}{and}\mspace{14mu}{no}\mspace{14mu}{retransmission}\mspace{14mu}{is}}\mspace{14mu}} \\{{pending}\mspace{14mu}{during}{\;\mspace{11mu}}{frame}\mspace{14mu}\left( {f + 1} \right)} \\{j_{m} = {\underset{r{({j;f})}}{\arg\mspace{11mu}\max}\left( {\beta_{e,{r{({j;f})}}}^{2} + \beta_{\theta,{r{({j;f})}}}^{2}} \right)\mspace{14mu}{\forall{j \in {S_{r}(f)}}}}}\end{matrix}$

The predicted transmit power needed for frame (f+1) can be written as:

$\begin{matrix}{{P_{e}\left( {{f + 1};f} \right)} = {{\xi \cdot \left( \frac{\beta_{e,j_{m}}^{2} + \beta_{\theta,j_{m}}^{2}}{\beta_{c}^{2}} \right)} +}} \\{\sum\limits_{j = 0}^{H - 1}\;{{I_{t}\left( {j;f} \right)} \cdot {q\left( {j;f} \right)} \cdot \left( \frac{\beta_{e,{\chi{({j;f})}}}^{2} + \beta_{\theta,{\chi{({j;f})}}}^{2}}{\beta_{c}^{2}} \right)}} \\{{P_{est}\left( {{f + 1};f} \right)} = {{P_{av}(f)} \cdot \left\lbrack {1 + {P_{e}\left( {{f + 1};f} \right)}} \right\rbrack}}\end{matrix}$

As noted above, this is the average transmit power that would be neededduring frame (f+1), rather than the peak power.

It is also possible to compute the peak transmit power that could beneeded and reserve power for the enhanced uplink channels in aprobabilistic way. In this case, the mobile station would first computethe possible power that could be needed in the next frame based onpending re-transmissions and rate requests. Then, for each possibility,the mobile station would probabilistically determine whether thecorresponding power would be needed or not. The mobile station wouldthen select from among all candidate possibilities the possibility thatrequires the maximum power. The mobile station assumes that this maximumpower will be needed throughout next frame, and performs TFC selectionaccording to the Release 99 methodology.

In block 430, the mobile station reserves power for the “minimum set” ofchannels on the Release 99 uplink. The uplink may carry various types ofdata, some of which have high priority and some of which have lowpriority. High priority data may, for example, include voice data,streaming video or other delay-sensitive data. Low priority data mayinclude various types of data that are not sensitive to transmissiondelays. The “minimum set” includes the high priority data that needs tobe transmitted without delay. Power is therefore reserved for theminimum set in this embodiment. Power is then also reserved for theexpected data transmissions on the enhanced uplink, as described above.

After power is reserved for the enhanced uplink transmissions, thehighest supported data rate for the Release 99 uplink is recomputedbased upon the power limits of the mobile station, minus the powerreserved for the enhanced uplink channels. This data rate is then usedfor the Release 99 uplink transmissions. The retransmissions of the HARQprocesses on the enhanced uplink use the same data rates that were usedwhen the processes were originally transmitted. This is necessarybecause the retransmitted data for the HARQ processes must be identicalto the originally transmitted data.

The recomputation of the highest supported data is performed as follows.Once the mobile station computes the average transmit power for theenhanced uplink channels, it needs to eliminate DPDCH TFC fromSUPPORTED_STATE in accordance with the priority rules.

Let us define:g_(d)(i)=Priority for DPDCH TFC iS_(d)(f)=Set of DPDCH TFC in Supported State at the end of frame fg_(e)(i)=Priority for E-DPDCH TF iS_(e)=E-DPDCH TFS

If DPDCH always has the highest priority, there is no issue, as shownbelow.

$\begin{matrix}{{S_{d,o}(f)} = \left\{ {{i:{{g_{d}(i)} < {{g_{e}(j)}\mspace{14mu}{\forall{i \in {S_{d}(f)}}}}}},{j \in S_{e}}} \right\}} \\{= {{Set}\mspace{14mu}{of}\mspace{14mu}{DPDCH}\mspace{14mu}{TFC}\mspace{14mu}{in}\mspace{14mu}{Supported}\mspace{14mu}{State}\mspace{14mu}{with}\mspace{14mu}{less}}} \\{{priority}\mspace{14mu}{than}\mspace{14mu} E\text{-}{DPDCH}} \\{\left. \Rightarrow{{If}\mspace{14mu}{S_{d,o}(f)}} \right. = \left. {{Null}\mspace{14mu}{set}}\Rightarrow{{No}\mspace{14mu}{issue}\mspace{14mu}{in}\mspace{14mu}{TFC}\mspace{14mu}{selection}} \right.} \\{{S_{d,o}^{c}(f)} = {{S_{d}(f)} - {S_{d,o}(f)}}} \\{= {{Complement}\mspace{14mu}{of}\mspace{14mu}{S_{d,o}(f)}}}\end{matrix}$

Define:

$\beta_{d,m} = {\max\limits_{i}\left\{ {\beta_{d,i}{\forall\;{i \in {S_{d,o}^{c}(f)}}}} \right\}}$

The expected available power for DPDCH TFC with lower priority thanE-DCH is:

${P_{d,o}\left( {{f + 1};f} \right)} = {\max\left\{ {{P_{\max} - {{P_{av}(f)} \cdot \left\lbrack {1 + \left( \frac{\beta_{d,m}}{\beta_{c}} \right)^{2} + {P_{e}\left( {{f + 1};f} \right)}} \right\rbrack}},0} \right\}}$

Therefore, we have:

$\mspace{40mu}\begin{matrix}{{\Psi_{d}\left( {f + 1} \right)} = {{S_{d,o}^{c}(f)}\bigcup\left\{ {i:{\beta_{d,i} < {{\sqrt{\frac{P_{d,a}\left( {{f + 1};f} \right)}{P_{av}(f)}} \cdot \beta_{c}}\mspace{14mu}{\forall\mspace{11mu}{i \in {S_{d,o}(f)}}}}}} \right\}}} \\{= {{Candidate}\mspace{14mu}{set}\mspace{14mu}{of}\mspace{14mu}{DPDCH}\mspace{14mu}{TFC}\mspace{14mu}{for}\mspace{14mu}{frame}\mspace{14mu}\left( {f + 1} \right)}}\end{matrix}$

The mobile station then chooses the DPDCH TFC from the candidate setshown above.

As noted above, although the foregoing description focuses onembodiments that are implemented in wireless communication systems thatare designed in accordance with 3GPP standards (particularly Release 99and Release 6,) other embodiments may be implemented in systems that donot meet these standards. Alternative embodiments of the invention mayvary from the above description in various other ways as well.

For example, in one embodiment, it is not necessary to reserve power forthe primary (e.g., Release 99) uplink prior to estimating the powerrequirements for the enhanced uplink channels. One method in accordancewith this embodiment would consist of estimating power requirements forpending HARQ processes on the enhanced uplink, reserving the estimatedamount of power for the pending HARQ processes, and then determining thehighest data rate that is supported on a primary uplink after power isreserved for the pending HARQ processes on the enhanced uplink.

Although not discussed in detail above, it should also be noted that themobile station or other wireless transceiver may be implemented byproviding suitable programs in a programmable device. The structure ofthe transceiver typically includes one or more processors that implementthe functionality of the device (such as probability tracking rateselection) by executing corresponding program instructions. Theseprogram instructions are typically embodied in a storage medium that isreadable by the one or more processors. Such a storage medium embodyingprogram instructions for implementing the functionality described aboveis an alternative embodiment of the invention.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans may implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

One or more of the steps of the methods and/or algorithms described inconnection with the embodiments disclosed herein may be interchangedwithout departing from the scope of the invention. The steps of a methodor algorithm described in connection with the embodiments disclosedherein may be embodied directly in hardware, in a software moduleexecuted by a processor, or in a combination of the two. A softwaremodule may reside in RAM memory, flash memory, ROM memory, EPROM memory,EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or anyother form of storage medium known in the art. An exemplary storagemedium is coupled to the processor such the processor can readinformation from, and write information to, the storage medium. In thealternative, the storage medium may be integral to the processor. Theprocessor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. In a wireless communication system configured to retransmit pendingdata until the data is acknowledged or until a maximum number ofretransmissions are made, a method comprising: determining probabilityvalues associated with numbers of attempted transmissions of data; foreach of a plurality of pending data transmissions, determining a numberof times transmission of the data transmission has been attempted on asecondary channel in one or more preceding frames, determining aprobability associated with the number of times the data transmissionhas been attempted, allocating power for the data transmission on thesecondary channel in a succeeding frame based upon the probabilityassociated with the number of times the data transmission has beenattempted, allocating power for data transmissions on a primary channel;and selecting a data rate for data transmissions on the primary channel,wherein selecting the data rate for transmission of data on the primarychannel comprises: selecting a highest supported data rate that is nogreater than a maximum data rate specified by a base station; andselecting a data rate based on a maximum power level without adjustmentfor allocating power for the secondary channel and then recomputing thedata rate for transmission of data on the primary channel based on themaximum power level minus the power allocated for the secondary channel.2. In a wireless communication system having a first reverse linkchannel on which data rate selection is performed between successivedata transmission frames and a second reverse link channel on which datais transmitted using an automatic retransmission mechanism, a methodcomprising: selecting an initial data rate for data transmissions on thefirst channel based on recent historical channel conditions and amaximum power level; estimating power requirements for datatransmissions on the second channel based on historical retransmissionprobabilities; reserving a first amount of power for transmission of aminimum set of data on the first channel based on the initial data rate;reserving a second amount of power for transmission of data on thesecond channel; and selecting final data rate for data transmissions onthe first channel based on recent historical channel conditions and apower level equal to the maximum power level minus the second amount ofpower.
 3. The method of claim 2, wherein the historical retransmissionprobabilities comprise probabilities with which data transmissions onthe second channel have to be retransmitted and corresponding numbers oftimes data transmissions on the second channel have been attempted. 4.The method of claim 3, wherein estimating power requirements for datatransmissions on the second channel comprises, for each pending datatransmission, identifying a number of times the data transmission hasbeen attempted, identifying the probability corresponding to the numberof attempted transmissions and estimating a power requirement for thedata transmission based on the identified probability.
 5. The method ofclaim 4, wherein estimating a power requirement for the datatransmission based on the identified probability comprises eitherestimating full power or no power for the data transmission based on theidentified probability.
 6. An apparatus comprising: a transceiverconfigured to communicate data via a wireless communication link;wherein the transceiver is configured to retransmit pending data on asecondary channel until the data is acknowledged or until a maximumnumber of retransmissions are made, and wherein the transceiver isfurther configured to; allocate power for transmission of data on aprimary channel; select a data rate for transmission of data on theprimary channel; select the data rate for transmission of data on theprimary channel by selecting a highest supported data rate that is nogreater than a maximum data rate specified by a base station; select thedata rate for transmission of data on the primary channel by selecting adata rate based on a maximum power level without adjustment forallocating power for the secondary channel and then recomputing the datarate for transmission of data on the primary channel based on themaximum power level minus the power allocated for the secondary channel;determine probability values associated with one or more numbers ofattempted data transmissions; and for each of a plurality of pendingdata transmissions, determine a number of times the data transmissionhas been attempted in one or more preceding frames, determine aprobability associated with the number of times the data transmissionhas been attempted, and allocate power for the data transmission in asucceeding frame based upon the probability associated with the numberof times the data transmission has been attempted.
 7. An apparatuscomprising: a transceiver for a wireless communication system; whereinthe transceiver is configured to transmit data on a first reverse linkchannel for which data rate selection is performed between successivedata transmission frames and on a second reverse link channel thatemploys an automatic retransmission mechanism; wherein the transceiveris further configured to select an initial data rate for datatransmissions on the first channel based on recent historical channelconditions and a maximum power level; wherein the transceiver isconfigured to estimate power requirements for data transmissions on thesecond channel based on historical retransmission probabilities; whereinthe transceiver is configured to reserve a first amount of power fortransmission of a minimum set of data on the first channel based on theinitial data rate; wherein the transceiver is configured to reserve asecond amount of power for transmission of data on the second channel;and wherein the transceiver is configured to select a final data ratefor data transmissions on the first channel based on the recenthistorical channel conditions and a power level equal to the maximumpower level minus the second amount of power.
 8. The apparatus of claim7, wherein the historical retransmission probabilities compriseprobabilities with which data transmissions on the second channel haveto be retransmitted and corresponding numbers of times datatransmissions on the second channel have been attempted.
 9. Theapparatus of claim 8, wherein the transceiver is configured to estimatepower requirements for data transmissions on the second channel for eachpending data transmission by identifying a number of times the datatransmission has been attempted, identifying the probabilitycorresponding to the number of attempted transmissions and estimating apower requirement for the data transmission based on the identifiedprobability.
 10. The apparatus of claim 9, wherein the transceiver isconfigured to estimate a power requirement for the data transmissionbased on the identified probability by either estimating full power orno power for the data transmission, based on the identified probability.